Update wasi-libc version in CI and implement custom sync primitives (#2028)

Update wasi-libc version to resolve the hang issue when running wasi-threads cases.

Implement custom sync primitives as a counterpart of `pthread_barrier_wait` to
attempt to replace pthread sync primitives since they seem to cause data races
when running with the thread sanitizer.

.github/workflows/compilation_on_android_ubuntu.yml

@@ -368,9 +368,9 @@ jobs:
           mkdir wasi-libc
           cd wasi-libc
           git init
-          # "Rename thread_spawn import" commit on main branch
+          # "Fix a_store operation in atomic.h" commit on main branch
           git fetch https://github.com/WebAssembly/wasi-libc \
-            8f5275796a82f8ecfd0833a4f3f444fa37ed4546
+            1dfe5c302d1c5ab621f7abf04620fae92700fd22
           git checkout FETCH_HEAD
           make -j \
             AR=/opt/wasi-sdk/bin/llvm-ar \
@@ -532,9 +532,9 @@ jobs:
           mkdir wasi-libc
           cd wasi-libc
           git init
-          # "Rename thread_spawn import" commit on main branch
+          # "Fix a_store operation in atomic.h" commit on main branch
           git fetch https://github.com/WebAssembly/wasi-libc \
-            8f5275796a82f8ecfd0833a4f3f444fa37ed4546
+            1dfe5c302d1c5ab621f7abf04620fae92700fd22
           git checkout FETCH_HEAD
           make -j \
             AR=/opt/wasi-sdk/bin/llvm-ar \

.github/workflows/compilation_on_sgx.yml

@@ -265,9 +265,9 @@ jobs:
           mkdir wasi-libc
           cd wasi-libc
           git init
-          # "Rename thread_spawn import" commit on main branch
+          # "Fix a_store operation in atomic.h" commit on main branch
           git fetch https://github.com/WebAssembly/wasi-libc \
-            8f5275796a82f8ecfd0833a4f3f444fa37ed4546
+            1dfe5c302d1c5ab621f7abf04620fae92700fd22
           git checkout FETCH_HEAD
           make \
             AR=/opt/wasi-sdk/bin/llvm-ar \

core/iwasm/libraries/lib-wasi-threads/test/common.h

@@ -6,11 +6,16 @@
 #include <stdlib.h>
 #include <stdio.h>
 #include <assert.h>
-#include <pthread.h>
 #include <stdbool.h>
 #include <unistd.h>
 #include <limits.h>
 
+#if USE_CUSTOM_SYNC_PRIMITIVES != 0
+#include "sync_primitives.h"
+#else
+#include <pthread.h>
+#endif
+
 #include "wasi_thread_start.h"
 
 typedef enum {

core/iwasm/libraries/lib-wasi-threads/test/global_lock.c

@@ -11,7 +11,12 @@
 #include <stdio.h>
 #include <assert.h>
 #include <stdbool.h>
+
+#if USE_CUSTOM_SYNC_PRIMITIVES != 0
+#include "sync_primitives.h"
+#else
 #include <pthread.h>
+#endif
 
 #include "wasi_thread_start.h"
 

core/iwasm/libraries/lib-wasi-threads/test/sync_primitives.h

@@ -0,0 +1,91 @@
+/*
+ * Copyright (C) 2023 Amazon.com Inc. or its affiliates. All rights reserved.
+ * SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+ */
+
+#include <stdbool.h>
+
+/* Mutex */
+
+typedef int pthread_mutex_t;
+
+int
+pthread_mutex_init(pthread_mutex_t *mutex, void *unused)
+{
+    *mutex = 0;
+    return 0;
+}
+
+int
+pthread_mutex_destroy(pthread_mutex_t *mutex)
+{
+    return 0;
+}
+
+static bool
+try_pthread_mutex_lock(pthread_mutex_t *mutex)
+{
+    int expected = 0;
+    return __atomic_compare_exchange_n(mutex, &expected, 1, false,
+                                       __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST);
+}
+
+int
+pthread_mutex_lock(pthread_mutex_t *mutex)
+{
+    while (!try_pthread_mutex_lock(mutex))
+        __builtin_wasm_memory_atomic_wait32(mutex, 1, -1);
+    return 0;
+}
+
+int
+pthread_mutex_unlock(pthread_mutex_t *mutex)
+{
+    __atomic_store_n(mutex, 0, __ATOMIC_SEQ_CST);
+    __builtin_wasm_memory_atomic_notify(mutex, 1);
+    return 0;
+}
+
+/* Barrier */
+
+typedef struct {
+    int count;
+    int num_threads;
+    int mutex;
+    int ready;
+} pthread_barrier_t;
+
+int
+pthread_barrier_init(pthread_barrier_t *barrier, void *unused, int num_threads)
+{
+    barrier->count = 0;
+    barrier->num_threads = num_threads;
+    barrier->ready = 0;
+    pthread_mutex_init(&barrier->mutex, NULL);
+
+    return 0;
+}
+
+int
+pthread_barrier_wait(pthread_barrier_t *barrier)
+{
+    bool no_wait = false;
+    int count;
+
+    pthread_mutex_lock(&barrier->mutex);
+    count = barrier->count++;
+    if (barrier->count >= barrier->num_threads) {
+        no_wait = true;
+        barrier->count = 0;
+    }
+    pthread_mutex_unlock(&barrier->mutex);
+
+    if (no_wait) {
+        __atomic_store_n(&barrier->ready, 1, __ATOMIC_SEQ_CST);
+        __builtin_wasm_memory_atomic_notify(&barrier->ready, count);
+        return 0;
+    }
+
+    __builtin_wasm_memory_atomic_wait32(&barrier->ready, 0, -1);
+    return 0;
+}

samples/wasi-threads/README.md

@@ -11,8 +11,6 @@ $ cmake ..
 $ make
 ...
 $ ./iwasm wasm-apps/no_pthread.wasm
-...
-$ ./iwasm wasm-apps/exception_propagation.wasm
 ```
 
 ## Run samples in AOT mode

samples/wasi-threads/wasm-apps/CMakeLists.txt

@@ -43,5 +43,4 @@ function (compile_sample SOURCE_FILE)
   )
 endfunction ()
 
-compile_sample(no_pthread.c wasi_thread_start.S)
+compile_sample(no_pthread.c wasi_thread_start.S)
-compile_sample(thread_termination.c wasi_thread_start.S)

samples/wasi-threads/wasm-apps/thread_termination.c

@@ -1,142 +0,0 @@
-/*
- * Copyright (C) 2022 Amazon.com Inc. or its affiliates. All rights reserved.
- * SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
- */
-#ifndef __wasi__
-#error This example only compiles to WASM/WASI target
-#endif
-
-#include <stdlib.h>
-#include <stdio.h>
-#include <assert.h>
-#include <pthread.h>
-#include <stdbool.h>
-#include <unistd.h>
-
-#include "wasi_thread_start.h"
-
-#define BUSY_WAIT 0
-#define ATOMIC_WAIT 1
-#define POLL_ONEOFF 2
-
-/* Change parameters here to modify the sample behavior */
-#define TEST_TERMINATION_BY_TRAP 0 /* Otherwise `proc_exit` termination */
-#define TEST_TERMINATION_IN_MAIN_THREAD 1 /* Otherwise in spawn thread */
-#define LONG_TASK_IMPL ATOMIC_WAIT
-
-#define TIMEOUT_SECONDS 10
-#define NUM_THREADS 3
-static pthread_barrier_t barrier;
-
-typedef struct {
-    start_args_t base;
-    bool throw_exception;
-} shared_t;
-
-void
-run_long_task()
-{
-#if LONG_TASK_IMPL == BUSY_WAIT
-    for (int i = 0; i < TIMEOUT_SECONDS; i++)
-        sleep(1);
-#elif LONG_TASK_IMPL == ATOMIC_WAIT
-    __builtin_wasm_memory_atomic_wait32(0, 0, -1);
-#else
-    sleep(TIMEOUT_SECONDS);
-#endif
-}
-
-void
-start_job()
-{
-    /* Wait for all threads (including the main thread) to be ready */
-    pthread_barrier_wait(&barrier);
-    run_long_task(); /* Task to be interrupted */
-    assert(false && "Thread termination test failed");
-}
-
-void
-terminate_process()
-{
-    /* Wait for all other threads (including main thread) to be ready */
-    printf("Waiting before terminating\n");
-    pthread_barrier_wait(&barrier);
-
-    printf("Force termination\n");
-#if TEST_TERMINATION_BY_TRAP == 1
-    __builtin_trap();
-#else
-    __wasi_proc_exit(33);
-#endif
-}
-
-void
-__wasi_thread_start_C(int thread_id, int *start_arg)
-{
-    shared_t *data = (shared_t *)start_arg;
-
-    if (data->throw_exception) {
-        terminate_process();
-    }
-    else {
-        printf("Thread running\n");
-
-        start_job();
-    }
-}
-
-int
-main(int argc, char **argv)
-{
-    int thread_id = -1, i;
-    shared_t data[NUM_THREADS] = { 0 };
-
-    if (pthread_barrier_init(&barrier, NULL, NUM_THREADS + 1) != 0) {
-        printf("Failed to init barrier\n");
-        return EXIT_FAILURE;
-    }
-
-    for (i = 0; i < NUM_THREADS; i++) {
-        /* No graceful memory free to simplify the example */
-        if (!start_args_init(&data[i].base)) {
-            printf("Failed to allocate thread's stack\n");
-            return EXIT_FAILURE;
-        }
-    }
-
-    /* Create a thread that forces termination through trap or `proc_exit` */
-#if TEST_TERMINATION_IN_MAIN_THREAD == 1
-    data[0].throw_exception = false;
-#else
-    data[0].throw_exception = true;
-#endif
-    thread_id = __wasi_thread_spawn(&data[0]);
-    if (thread_id < 0) {
-        printf("Failed to create thread: %d\n", thread_id);
-        return EXIT_FAILURE;
-    }
-
-    /* Create two additional threads to test exception propagation */
-    data[1].throw_exception = false;
-    thread_id = __wasi_thread_spawn(&data[1]);
-    if (thread_id < 0) {
-        printf("Failed to create thread: %d\n", thread_id);
-        return EXIT_FAILURE;
-    }
-    data[2].throw_exception = false;
-    thread_id = __wasi_thread_spawn(&data[2]);
-    if (thread_id < 0) {
-        printf("Failed to create thread: %d\n", thread_id);
-        return EXIT_FAILURE;
-    }
-
-#if TEST_TERMINATION_IN_MAIN_THREAD == 1
-    printf("Force termination (main thread)\n");
-    terminate_process();
-#else  /* TEST_TERMINATION_IN_MAIN_THREAD */
-    printf("Main thread running\n");
-
-    start_job();
-#endif /* TEST_TERMINATION_IN_MAIN_THREAD */
-    return EXIT_SUCCESS;
-}